1. Field of the Invention
The invention is directed to the 3-ethoxypropionate esters of cyclaradine useful in the treatment of certain viral infections. Additionally, the invention involves orally, parenertally and topically acceptable formulations of the esters and method of utilizing same to treat susceptible viral infections.
2. Description of the Prior Art
U.S. Pat. No. 4,362,729 (R. Vince) discloses (C.sub.1 -C.sub.6)alkoxy(C.sub.1 -C.sub.6)alkanoyl esters of (.+-.)-cyclaradine and topically acceptable antiviral formulations useful for treating susceptible viral infections. Only the methoxyacetate ester is specifically disclosed.
U.S. Pat. No. 4,138,562, issued Feb. 6, 1979, and J. Med. Chem., 20, 612, (1977) discloses the synthesis of the nucleoside(.+-.)-9-[2.alpha.,3.beta.-dihydroxy-4.alpha.-(hydroxymethyl)cyc lopent-1.alpha.-yl]adenine which will hereinafter be referred to more simply as (.+-.)cyclaradine. (.+-.)-Cyclaradine is the parent racemic alcohol of the 3-ethoxypropionate ester of this invention. The parent racemic alcohol and the simple alkanoate esters thereof are the subject of U.S. Pat. No. 4,268,672, issued May 19, 1981.
Cyclaradine, in its racemic and optically active forms, exhibits potent antiviral activity, in vitro, against viral pathogens such as Herpes and is resistant to the enzyme adenosine deaminase (a normal constituent of human serum) which is responsible for the destruction of the antiviral properties of currently available antiviral nucleosides such as 9-.beta.-D-arabinofuranosyladenine. It has subsequently been found, however, that cyclaradine and its simple alkyl esters are significantly more active in vivo than expected. Moreover, U.S. Pat. No. 4,302,729 discloses that the alkoxyalkanoate esters, and specifically the methoxyacetate ester are only active topically.